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<meta name="description" content="######1). 生命周期相关函数  函数    | 说明 | — | — |void componentWillMount()    |该函数只会被执行一次，在初始化渲染之前执行，它执行完成之后，render函数会马上被React Native框架调用|ReactClass render()    | 该函数会被执行多次，返回我们的UI组件信息|void componentDidMount()">
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<meta property="og:description" content="######1). 生命周期相关函数  函数    | 说明 | — | — |void componentWillMount()    |该函数只会被执行一次，在初始化渲染之前执行，它执行完成之后，render函数会马上被React Native框架调用|ReactClass render()    | 该函数会被执行多次，返回我们的UI组件信息|void componentDidMount()">
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<meta name="twitter:description" content="######1). 生命周期相关函数  函数    | 说明 | — | — |void componentWillMount()    |该函数只会被执行一次，在初始化渲染之前执行，它执行完成之后，render函数会马上被React Native框架调用|ReactClass render()    | 该函数会被执行多次，返回我们的UI组件信息|void componentDidMount()">
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          <h1 class="post-title" itemprop="name headline">React-Native-Component生命周期</h1>
        

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        <p>######1). 生命周期相关函数<br>  函数    | 说明 |<br> — | — |<br>void componentWillMount()    |该函数只会被执行一次，在初始化渲染之前执行，它执行完成之后，render函数会马上被React Native框架调用|<br>ReactClass render()    | 该函数会被执行多次，返回我们的UI组件信息|<br>void componentDidMount()    |该函数之后执行一次，在组件初始化渲染完成之后被调用|<br>void componentWillReceiveProps(nextProps)    | ReactNative组件收到新的props时，这个函数会被回调，回调的参数nextProps就是新的props|<br>bool shouldComponentUpdate(nextProps, nextState)    |ReactNative组件收到新的props或者新的state时，这个函数将被调用，它接收2个参数，第一个是新的props,第二个是新的state，这个函数还需要返回一个bool值，用来告诉ReactNative框架针对这次改变，ReactNative是否需要重新渲染本组件|<br>void componentWillUpdate(nextProps, nextState)    |在ReactNative框架重新渲染ReactNative组件之前会调用这个函数。开发者可以在和这个函数中为即将发生的重新渲染做一些准备，但开发者不能在这个函数中通过this.setState再次改变状态机变量的值|<br>void componentDidUpdate(prevProps, prevState)    |React Native框架在重新渲染ReactNative组件完成之后调用这个函数，传入两个参数时渲染前的props和state|<br>void componentWillUnmount()    |在React Native组件被卸载之前这个函数将执行|</p>
<a id="more"></a>
<p>######2). 执行流程<br>I. 首次进入：componentWillMount -&gt; render -&gt; componentDidMount<br>II. 改变state：shouldComponentUpdate -&gt; componentWillUpdate -&gt; render -&gt; componentDidUpdate<br>III. 改变props：componentWillReceiveProps -&gt; shouldComponentUpdate -&gt; componentWillUpdate -&gt; render -&gt; componentDidUpdate<br>IV. 页面销毁：componentWillUnmount</p>
<p>######3). 测试代码<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span 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class="line">121</span><br><span class="line">122</span><br><span class="line">123</span><br><span class="line">124</span><br><span class="line">125</span><br><span class="line">126</span><br><span class="line">127</span><br><span class="line">128</span><br><span class="line">129</span><br><span class="line">130</span><br><span class="line">131</span><br><span class="line">132</span><br><span class="line">133</span><br><span class="line">134</span><br><span class="line">135</span><br><span class="line">136</span><br><span class="line">137</span><br><span class="line">138</span><br><span class="line">139</span><br><span class="line">140</span><br><span class="line">141</span><br><span class="line">142</span><br><span class="line">143</span><br><span class="line">144</span><br><span class="line">145</span><br><span class="line">146</span><br><span class="line">147</span><br><span class="line">148</span><br><span class="line">149</span><br><span class="line">150</span><br></pre></td><td class="code"><pre><span class="line">import React, &#123;Component&#125; from &apos;react&apos;;</span><br><span class="line">import &#123;</span><br><span class="line">	Button,</span><br><span class="line">	StyleSheet, Text,</span><br><span class="line">	View</span><br><span class="line">&#125; from &apos;react-native&apos;;</span><br><span class="line"></span><br><span class="line">/**</span><br><span class="line"> * @FileName: ComponentLifecycle</span><br><span class="line"> * @Author: mazaiting</span><br><span class="line"> * @Date: 2018/6/13</span><br><span class="line"> * @Description: 组件的声明周期</span><br><span class="line"> */</span><br><span class="line">class ComponentLifecycle extends Component &#123;</span><br><span class="line">	/**</span><br><span class="line">	 * 1. 定义属性的默认值</span><br><span class="line">	 * 调用时使用this.props.value</span><br><span class="line">	 * @type &#123;&#123;value: string&#125;&#125;</span><br><span class="line">	 */</span><br><span class="line">	static defaultProps = &#123;</span><br><span class="line">		value: &apos;mazaiting&apos;</span><br><span class="line">	&#125;;</span><br><span class="line">	</span><br><span class="line">	/**</span><br><span class="line">	 * 2. 构造函数</span><br><span class="line">	 * @param props</span><br><span class="line">	 */</span><br><span class="line">	constructor(props) &#123;</span><br><span class="line">		super(props);</span><br><span class="line">		/**</span><br><span class="line">		 * 初始化状态</span><br><span class="line">		 * @type &#123;&#123;value: string&#125;&#125;</span><br><span class="line">		 */</span><br><span class="line">		this.state = &#123;</span><br><span class="line">			value: &apos;initial state.&apos;</span><br><span class="line">		&#125;</span><br><span class="line">	&#125;</span><br><span class="line">	</span><br><span class="line">	/**</span><br><span class="line">	 * 3. 挂载组件，该函数在组件的声明周期中只执行一次</span><br><span class="line">	 */</span><br><span class="line">	componentWillMount() &#123;</span><br><span class="line">		console.log(&apos;componentWillMount&apos;)</span><br><span class="line">	&#125;</span><br><span class="line">	</span><br><span class="line">	/**</span><br><span class="line">	 * 4. 渲染界面</span><br><span class="line">	 */</span><br><span class="line">	render() &#123;</span><br><span class="line">		console.log(&apos;render&apos;);</span><br><span class="line">		return (</span><br><span class="line">			&lt;View style=&#123;styles.container&#125;&gt;</span><br><span class="line">				&lt;Text&gt;属性初始值：&#123;this.props.value&#125; &#123;&apos;\n&apos;&#125; 状态初始值：&#123;this.state.value&#125;&lt;/Text&gt;</span><br><span class="line">				&lt;Button</span><br><span class="line">					title=&#123;&apos;改变state&apos;&#125;</span><br><span class="line">					onPress=&#123;() =&gt; &#123;</span><br><span class="line">						this.setState(&#123;value: &apos;changed&apos;&#125;)</span><br><span class="line">					&#125;&#125;</span><br><span class="line">				/&gt;</span><br><span class="line">			&lt;/View&gt;</span><br><span class="line">		)</span><br><span class="line">	&#125;</span><br><span class="line">	</span><br><span class="line">	/**</span><br><span class="line">	 * 5. 完成组件挂载，该函数在组件的声明周期中只执行一次</span><br><span class="line">	 */</span><br><span class="line">	componentDidMount() &#123;</span><br><span class="line">		console.log(&apos;componentDidMount&apos;)</span><br><span class="line">	&#125;</span><br><span class="line">	</span><br><span class="line">	/**</span><br><span class="line">	 * 组件渲染完成，接收到新的props时，函数被调用</span><br><span class="line">	 * @param nextProps 新配置</span><br><span class="line">	 */</span><br><span class="line">	componentWillReceiveProps(nextProps) &#123;</span><br><span class="line">		console.log(&apos;componentWillReceiveProps：&apos; + nextProps.value)</span><br><span class="line">	&#125;</span><br><span class="line">	</span><br><span class="line">	/**</span><br><span class="line">	 * PureComponent不能重写此方法，只能在Component中重写</span><br><span class="line">	 * 组件接收到新的state或props时，函数被调用</span><br><span class="line">	 * @param nextProps 新的配置</span><br><span class="line">	 * @param nextState 新的状态</span><br><span class="line">	 * @return 是否重新渲染本组件</span><br><span class="line">	 */</span><br><span class="line">	shouldComponentUpdate(nextProps, nextState) &#123;</span><br><span class="line">		console.log(&apos;shouldComponentUpdate&apos;);</span><br><span class="line">		return true</span><br><span class="line">	&#125;</span><br><span class="line">	</span><br><span class="line">	/**</span><br><span class="line">	 * 准备更新组件</span><br><span class="line">	 * @param nextProps 新配置</span><br><span class="line">	 * @param nextState 新状态</span><br><span class="line">	 */</span><br><span class="line">	componentWillUpdate(nextProps, nextState) &#123;</span><br><span class="line">		console.log(&apos;componentWillUpdate&apos;)</span><br><span class="line">	&#125;</span><br><span class="line">	</span><br><span class="line">	/**</span><br><span class="line">	 * 组件更新完成</span><br><span class="line">	 * @param prevProps 之前的配置</span><br><span class="line">	 * @param prevState 之前的状态</span><br><span class="line">	 */</span><br><span class="line">	componentDidUpdate(prevProps, prevState) &#123;</span><br><span class="line">		console.log(&apos;componentDidUpdate&apos;)</span><br><span class="line">	&#125;</span><br><span class="line">	</span><br><span class="line">	/**</span><br><span class="line">	 * 组件被卸载之前调用</span><br><span class="line">	 */</span><br><span class="line">	componentWillUnmount() &#123;</span><br><span class="line">		console.log(&apos;componentWillUnmount&apos;)</span><br><span class="line">	&#125;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line">/**</span><br><span class="line"> * 样式属性</span><br><span class="line"> */</span><br><span class="line">const styles = StyleSheet.create(&#123;</span><br><span class="line">	container: &#123;</span><br><span class="line">		backgroundColor: &apos;#DDD&apos;</span><br><span class="line">	&#125;</span><br><span class="line">&#125;);</span><br><span class="line"></span><br><span class="line">/**</span><br><span class="line"> * 测试改变ComponentLifecycle组件的props后的回调函数是否执行</span><br><span class="line"> */</span><br><span class="line">class ComponentLifecycleWrapper extends Component &#123;</span><br><span class="line">	state=&#123;</span><br><span class="line">		value: &apos;from parent&apos;</span><br><span class="line">	&#125;;</span><br><span class="line">	render() &#123;</span><br><span class="line">		return(</span><br><span class="line">			&lt;View style=&#123;styles.container&#125;&gt;</span><br><span class="line">				&lt;ComponentLifecycle &#123;...this.state&#125;/&gt;</span><br><span class="line">				&lt;Button</span><br><span class="line">					title=&apos;改变props&apos;</span><br><span class="line">					onPress=&#123;() =&gt; &#123;</span><br><span class="line">						this.setState(&#123;</span><br><span class="line">							value: &apos;changed&apos;</span><br><span class="line">						&#125;)</span><br><span class="line">					&#125;&#125;</span><br><span class="line">				/&gt;</span><br><span class="line">			&lt;/View&gt;</span><br><span class="line">		)</span><br><span class="line">	&#125;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line">AppRegistry.registerComponent(&apos;abcd&apos;, () =&gt; ComponentLifecycleWrapper);</span><br></pre></td></tr></table></figure></p>
<p>######4). 界面<br><img src="https://upload-images.jianshu.io/upload_images/3110861-f1e3f6487d232420.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240" alt="图1.png"></p>
<p>######5). 首次进入<br><img src="https://upload-images.jianshu.io/upload_images/3110861-08b442e352c91841.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240" alt="图2.png"></p>
<p>######6). 改变state<br><img src="https://upload-images.jianshu.io/upload_images/3110861-dbc7f992a07a0fce.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240" alt="图3.png"></p>
<p>######7). 改变props<br><img src="https://upload-images.jianshu.io/upload_images/3110861-ccf5ecf7845416e2.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240" alt="图4.png"></p>
<p>######8). 整个的一个流程<br><img src="https://upload-images.jianshu.io/upload_images/3110861-67efa74f2c3f7dc6.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240" alt="图5.png"></p>
<p>######9). state(状态) 和 props(属性)<br>React Native使用state和props来控制组件<br>I. props</p>
<ul>
<li><p>属性静态指定</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">static defaultProps = &#123;</span><br><span class="line">	value: &apos;mazaiting&apos;</span><br><span class="line">&#125;;</span><br></pre></td></tr></table></figure>
</li>
<li><p>属性动态传入</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line">class Greeting extends Component &#123;</span><br><span class="line">  render() &#123;</span><br><span class="line">    return (</span><br><span class="line">      &lt;Text&gt;Hello &#123;this.props.name&#125;!&lt;/Text&gt;</span><br><span class="line">    );</span><br><span class="line">  &#125;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line">export default class LotsOfGreetings extends Component &#123;</span><br><span class="line">  render() &#123;</span><br><span class="line">    return (</span><br><span class="line">      &lt;View style=&#123;&#123;alignItems: &apos;center&apos;&#125;&#125;&gt;</span><br><span class="line">        &lt;Greeting name=&apos;Rexxar&apos; /&gt;</span><br><span class="line">      &lt;/View&gt;</span><br><span class="line">    );</span><br><span class="line">  &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
</li>
</ul>
<p>II. state</p>
<ul>
<li><p>初始化<br>在构造函数中去初始化state</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">constructor(props) &#123;</span><br><span class="line">	super(props);</span><br><span class="line">	/**</span><br><span class="line">	 * 初始化状态</span><br><span class="line">	 * @type &#123;&#123;value: string&#125;&#125;</span><br><span class="line">	 */</span><br><span class="line">	this.state = &#123;</span><br><span class="line">		value: &apos;initial state.&apos;</span><br><span class="line">	&#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
</li>
<li><p>修改值<br>在组件中使用this.setState()方法来修改状态值，当状态被修改后，界面会被自动更新</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">this.setState(&#123;value: &apos;changed&apos;&#125;)</span><br></pre></td></tr></table></figure>
</li>
</ul>
<p>####<a href="https://reactjs.org/docs/state-and-lifecycle.html" target="_blank" rel="noopener">React 生命周期–官网地址</a></p>
<p>####<a href="https://gitee.com/mazaiting/React-Native-Study" target="_blank" rel="noopener">代码下载</a></p>

      
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